Note: Descriptions are shown in the official language in which they were submitted.
W0 95105322 216 84 62
PCT/GB94/01753
1
CONTAINER CLOSURE ASBEMBLY
This invention relates to a container closure assembly.
In particular it relates to such an assembly for pressurised
containers, and it is especially suitable for containers for
carbonated, fizzy and pressurised drinks as well as any
liquids or other contents which may be under pressure in a
container.
In certain circumstances high internal pressures can
force conventional closures violently from the neck, and
this risks injury or damage. This can be a particular
problem when, for example, a fizzy drinks container is
opened for the first time. The contents are often highly
pressurised so that the drink will retain a good "fizz".
The pressure can often dramatically increase if the
container has been heated up or knocked or shaken prior to
opening. The problem is made worse in closure assemblies
employing short screw threads or fast pitch threads such as
90° closure threads, since such designs are intended to make
the closure easy to remove from the neck.
The present invention provides a container closure
assembly for storing solids or fluids under pressure, said
assembly comprising:
a container neck;
a closure for said neck;
a first screw thread on one of said neck and closure;
a second screw thread on another of said neck and
closure; said second screw thread being engageable with said
first screw thread;
means for forming a seal between said neck and closure
when said closure is screwed down on said neck;
mutually engageable elements on said neck and closure
to block or restrict rotation of said closure in an
unscrewing direction beyond an intermediate position when
said closure is under an axial pressure in a direction
emerging from said container neck;
wherein said neck .and closure are constructed and
arranged to provide a vent for venting gas from said
216$462
z
container neck at least when said closure is in said
intermediate position, and wherein the first thread (14)
comprises a plurality of first thread segments, and the
second thread (16) comprises a plurality of second thread
segments, that are movable along a continuous helical thread
path defined between the first thread segments, whereby the
closure (12) can be moved from a fully released to a fully
closed position on the neck (10) by a single smooth rotation
through 360° or less.
Preferably, the thread on one of the neck and closure
has a wider portion at the end adjacent to its respective
opening, and the thread of the other of the neck and the
closure is narrower than the thicker portion of the other
thread, whereby when the closure is removed from the closed
position, pressure is released through the space between the
threads on said one of the neck and the closure.
It can be seen that the _present invention solves the
above-stated technical problem by the provision of blocking
means on the neck and closure to block temporarily the
unscrewing of the closure at a partially unscrewed position
while excess pressure is allowed to vent from inside the
container. The stop means is configured such that the force
required to unblock the closure from its intermediate
position increases with increasing gas pressure in the
container. Preferably, the screw threads on the container
neck and closure are dimensioned such that a helical venting
pathway is left between the neck and closure threads,
whereby excess pressure inside the container vents out
between the said threads as soon as the seal between the
container and closure is broken, but before unscrewing of
the closure is completed. More preferably, venting takes
place along a path between the screw threads while the
closure is blocked by the blocking means at its intermediate
safety position. Preferably, transverse notches are
provided through the threads on the neck and the closure, of
the kind conventionally known in the art, to provide
additional gas venting in the intermediate position.
Such arrangements avoid any tendency for the internal
AMENDED SHE~1'
21 b8462
2 ct
pressure to force the closure off the container neck once a
person has begun to unscrew the closure and before venting
of excess gas from the container is complete.
The invention has been devised such that it is
especially suitable for carbonated beverage containers
however, it will be appreciated that the invention may find
use as a pressure safety closure in other fields relating to
pressurised closure assemblies.
AMENDED SHEfT
21684b~
W0 95/05322 PCT/GB94/01753
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r~l nc»ro accctnhl ; o~
Preferably, the means for permitting rotation and for
blocking or restricting rotation beyond the intermediate
position does not act to block or restrict rotation of the
closure when it is not substantially under axial pressure in
a direction emerging from the container neck. In this way,
the pressure safety feature is pressure responsive, and does
not block rotation of the closure when opening or closing
the container when the closure is not under pressure, for
example, when the contents of the container have become
substantially or completely depressurised.
Preferably, the arrangement of at least a portion of the
screw thread on the closure and at least a portion of the
screw thread on the neck is such as to permit limited axial
movement or displacement of the closure relative to the neck
without rotation of the closure when the closure is near or
at the intermediate position on the neck. With such an
arrangement, any internal pressure in the container will
tend to "lift" or displace the closure axially in a
direction emerging from the container neck.
Preferably, the means for permitting rotation and for
blocking or restricting rotation beyond the intermediate
position is responsive to axial displacement of the closure,
as allowed by the threads when the closure is near or at the
intermediate position. Preferably, the blocking or
restricting action comes into effect when the closure is
displaced axially in the direction emerging from the
container neck, and the blocking or restricting action does
not take effect when the closure is not displaced in the
direction emerging from the container neck. Preferably, the
blocking or restricting action can only be overcome or
released by applying an external downward axial force to the
closure to counter the internal pressure displacing the
closure axially upward, whereby the closure is moved back
into its non-displaced condition. The closure can then
easily be unscrewed past the intermediate position to open
the container.
Such an arrangement is therefore responsive not only to
2168462
WO 95/05322 PCT/GB94101753
4
internal pressure acting on the closure, but also to
external pressure applied by the person unscrewing the
closure. The safety feature is in one respect dependent on
the strength of the person unscrewing the closure. For
example, a child might be at most risk with a conventional
closure because he might not be able to grip the closure
very tightly, and a conventional closure might spin off
uncontrollably under high pressure. However, with the
arrangement described above, the closure will be held at the
intermediate position until the internal pressure has
reduced to a low level at which the child can release the
closure. On the other hand, a relatively strong adult might
be less at risk than a child with a conventional closure
because an adult would have a stronger grip to prevent a
conventional closure from spinning off uncontrollably. In
a similar fashion an adult would also be able to exert a
greater external downward axial force to release the
blocking effect of the invention at an earlier stage.
Nevertheless, should the closure begin to spin
uncontrollably when it is first unscrewed, the arrangement
will act to hold the closure at the intermediate position
until the pressure is reduced.
Preferably the means for permitting rotation and for
blocking or restricting rotation of the closure comprise at
least one first element on the neck which is engageable with
at least one second element on the closure to form an
abutment stop.
Preferably the means for permitting rotation and for
blocking or restricting rotation of the closure are formed
integrally with, or as part of, the screw thread on the neck
and/or with the screw thread on the closure.
Preferably, the mutually engageable elements comprise
a step or recess formed in the side of the first or second
screw thread to provide an abutment surface against which
the second or first thread abuts to block or restrict
rotation of the closure in an unscrewing direction at the
intermediate position when the closure is under axial
pressure from the contents of the container. More
W O 95/05322
PCT/GB94/01753
preferably, complementary steps or recesses for mutual
abutment are provided on both of the first and second screw
threads.
In the preferred embodiment, a first screw thread is
5 carried on one of the neck and the closure, and a second
screw thread is carried on the other of the neck and the
closure. The first thread is formed with a step profile
along at least one edge, in order to provide a first
abutment surface to engage a portion of the second thread
when the closure is unscrewed and is displaced axially in a
direction emerging from the container neck, and the second
thread has generally smooth edges, and one end of the second
thread acts as a second abutment surface to engage the first
abutment surface.
A preferred feature in the embodiment is that the
aforementioned abutment surfaces are not flat, but instead
are preferably formed with complementary indented (eg.
concave) and projecting (eg. convex) surfaces at least in an
axial plane, to nest one within the other whilst at the same
time providing profiles to assist smooth opening when the
pressure is released. For example, the first abutment
surface of the first thread may be curved or angled to be
flat or concave, and the second abutment surface of the
closure thread may comprise a convex end surface of the
closure thread. Such an arrangement provides an additional
safety feature in preventing the possibility that the
abutment surfaces might, under strong pressure or with wear,
creep past one another to allow the closure to rotate past
the intermediate position. The nesting of one abutment
surface within the other provides a hook to locate the
surfaces together positively, and the positive locating
effect will be stronger the higher the internal pressure to
which the closure is subjected.
Preferably, the screw thread on the container neck is
integrally formed in two portions. The first portion,
adjacent the top of the container has a first, wide cross
section. The second portion below the first portion has a
second, narrower cross-section. The transition between the
WO 95/05322 216 8 ~ 6 ~ pCT/GB94/01753
6
first and second portions provides a step on the lower
surface of the neck thread against which an end of the
closure thread abuts when the closure is unscrewed under
axial pressure from gas inside the container. The upper
surface of the neck thread is substantially continuous,
whereby unscrewing of the closure (and screwing down of the
closure) proceeds smoothly in the absence of axial pressure
from inside the container.
The container closure assembly may include means for
restricting or blocking rotation at a plurality of
intermediate positions between the closed position of the
closure and its fully released position.
The container and closure assembly of this invention may
comprise only single start screw threads, or it may
preferably comprise multi-start screw threads. More
preferably, the screw threads comprise four starts. In such
a case, the means for permitting rotation and for
restricting or blocking rotation beyond the predetermined
position may be associated with all of the screw threads in
the multi-start arrangement, or it may be associated with
only one or some of the threads. In the preferred
embodiment, a respective means for permitting rotation and
for restricting or blocking rotation is provided for each
thread segment of multi-start threads.
The means for venting internal pressure when the closure
is in its intermediate position may comprise means for
allowing the pressure to escape between the neck and the
closure, for example, by passage through or around the screw
threads. In the preferred embodiment, the arrangement of
the threads provides a clear escape passage along a helical
path between the threads when the closure is being
restrained at it intermediate position. Preferably, a
further gas venting path is provided by means of transverse
gas venting grooves extending across the neck and closure
threads, as is conventionally known in the art.
Preferably, the first thread includes first thread
portions at least parts of which are separated by a first
thread spacing having a first cross-sectional area, and the
W O 95!05322 ~ ~ 6 8 4 6 2 PCT/GB94/01753
7
second thread includes second thread portions having a
second cross-sectional area smaller than the first cross-
sectional area, thereby providing a vent clearance between
the first and second threads to permit venting of internal
pressure from the container along a path between the first
and second threads.
Additionally or alternatively, mutually alignable
venting passages similar to those conventionally used in
carbonated beverage container closure assemblies may be
provided in the closure and the neck threads to allow the
pressure to escape when the passages are aligned. Such
venting passages may be provided in segments of the screw
threads, the passages becoming aligned when the closure
reaches the intermediate positian.
The gas pressure release means and intermediate blocking
means according to the present invention is especially
useful in conjunction with closures that are screwed
completely onto the container neck by rotation through about
90° or less. Such closures have steeply pitched threads
that are more prone to blow off under pressure than
multiple-turn threads. the steep pitch of such threads can
also cause problems because the closures can work loose
during handling of the container closure assembly,
especially if the contents of the container are pressurised.
Therefore, the container closure assembly according to the
present invention preferably comprises locking means on the
container and closure to retain the closure tightly on the
container neck until a positive unscrewing torque is applied
to the closure. Preferably, the locking means comprises a
plurality of locking elements on the container neck and a
plurality of axial locking ribs on the inside of the skirt
of the closure. More preferably, the locking elements have
a locking surface that is inclined at an angle to a radius
of the container neck and the locking rib rests on the said
surface when the closure is in the closed position, whereby
pressure between the locking rib and the said surface tends
to urge the closure into the closed position. This helps to
ensure a gas-tight seal between the closure and the
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8
container neck. Such locking and urging means are described
in detail in international patent application no.
PCT/GB92/01255 (published as W093/01098).
5 The neck of the container. preferably has a smooth and
slightly rounded lip to permit drinking directly from the
container. Preferably, a gas-tight seal between the neck
and the closure in the screwed-down position is formed by
abutment between this lip and the inside of the base of the
10 closure. In order to allow for slightly variable
manufacturing tolerances, the inside of the base of the
closure is preferably provided with a compressible gas-tight
wad., or a layer of gas-tight elastomer, to assist in making
the said gas-tight seal. Alternatively, or additionally,
15 other gas-tight seals may be formed between the container
and the closure, e.g. interference fit seals, O-ring seals,
or plug seals formed by plugs depending from the base of the
closure and sealing against an inner surface of the neck, as
commonly known in the art.
20 In other preferred embodiments, the assembly further
comprises a circumferential sealing rib of substantially
triangular cross-section projecting from a first surface on
the neck or closure for abutment against a second surface on
the closure or the neck to form a pressure-tight seal
25 therewith when the closure is screwed down. The sealing rib
may, for example, project upwardly from the lip of the
container neck for abutment against the base of the closure.
Preferably, the sealing lip projects outwardly from a side
surface of the neck, or projects inwardly from a side
30 surface of the closure. In that case, the first and/or
second surface is preferably tapered (i.e. chamfered or
bevelled) an angle of from 2 to 20° from the longitudinal
axis of the assembly. This results in an improved pressure-
tight seal when the closure is screwed down.
35 Preferably, the sealing rib has a height of from 0.025
mm to 1.00 mm, more preferahly 0.025 to 0.25 mm.
Preferably, the sealing rib projects outwardly from the
lip of the container neck. this enables the sealing rib
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' ' W0951053~22 ' ~ ~~ PCTIGB94/01753
9
also to function as a drip reducer when liquids are poured
from inside the container. More preferably, one side of the
triangular cross-section of the sealing rib is substantially
flush with the top of the container neck and preferably also
perpendicular to the longitudinal axis of the container
neck.
The first and second screw threads may be of square or
rectangular or rounded cross section, as commonly known in
the art. Preferably, at least part of at least one of the
neck and closure screw threads has a substantially
triangular cross-section, since such cross-sections are easy
to bump off a mould when the container and closure are
formed by automated mass-production injection moulding or
blow-moulding.
The invention may additionally include any of the
features described in our published International patent
applications Nos. PCT/GB91/00850 (published as WO-A-
91/18799)~ PCT/GB92/01255 (published as WO-A-93/01098),
and PCT/GB93/02341 (published as W094/11267).I
', In particular, the closure may
be securable or removable by relative rotation of about 360°
or less, or preferably about 180° or less, or most
preferably about 90° or less.
Specific embodiments of the invention will now be
described by way of example with reference to the
accompanying drawings in which:
Figs 1 shows a side elevation view of a container
closure assembly according to the present invention with the
closure screwed down in the sealing position. The closure
is shown partly cut away and partly in cross-section;
Fia. 2 shows a side elevation view of the container
closure assembly of Fig. 1 after removal of the closure;
Fig. 3 shows a plane projection of the screw threads of
the container neck of Fig. 1, with the screw threads of the
closure- shown in phantom and the closure in the screwed
down, sealing position;
Fiq. 4 shows a similar projection to Fig. 3, but with
WO 95/05322 b ~ PCT/GB94/01753
the screw threads of the closure in the partially unscrewed,
blocked, gas-venting position;
Fig. 5 shows a similar projection to Figs. 3 and 4, but
with the screw threads of the closure in the unblocked
5 screwing/unscrewing position.
Fig_. 6 shows a projection similar to Figs. 3-5 of the
neck of a second embodiment of the present invention having
triangular/trapezoidal screw threads; and
Fiq. 7 shows a cross section through the neck and
10 closure of the embodiment of Fig. 6 taken perpendicular to
the threads.
Referring to Fig. 1, the assembly includes a container
neck 10 of a container 11 for carbonated beverages, and a
closure 12, both of plastics. The container 11 and closure
12 are formed by blow moulding and injection moulding from
PET and polyethylene respectively, in known fashion. The
neck carries a four-start first screw thread 14, and the
closure carries a corresponding four start second screw
thread 16. In this particular embodiment the threads have
square or rectangular cross section. The detail of these
threads will be described below. The threads provide
approximately a quarter turn (90°) of rotation of the
closure 12 relative to the neck 10 to move the closure from
fully closed to fully released.
The assembly includes locking means to retain the
closure 10 positively in its fully closed position on the
neck. The locking means comprise a pair of neck elements 18
spaced at 180° and projecting radially outwardly from the
neck and which are engageable with respective ones of four
axial closure ribs 20 which project radially inwardly from
an inner surface of the closure 10. The detail of such
locking means is described in our published patent
applications Nos. PCT/GB91/00850 (published as WO-A-
91/18799) and PCT/GB92/01255 (published as WO-A-93/01098).
The locking means can be overcome by application of an
external torque in a direction to unscrew the closure. In
this exemplary embodiment, the locking elements 18 have
respective abutment surfaces 19 which are inclined relative
CA 02168462 2004-10-28
' ' WO 951~53r2 ~ ~ ? PCTlGB94l01753
11
to the radial direction in order to provide a resilient
carrying action to urge the closure 12 into its fully closed
position.
The assembly also includes sealing means to form a
pressure-tight seal between the closure 12 and the neck 10
when the closure is in its fully closed position. The
sealing means comprises a layer of elastomer-13 of the type
conventionally used in this art provided on the inside
surface of the base of the closure 12. The layer_13 of
elastomer presses against a top surface 15 of the neck 10 to
form a gas-tight seal. Even very slight unscrewing of the
closure will release this seal and allow gas from inside the
container 11 to vent past the screw threads 14,16 to the
atmosphere.
The container closure assembly is also provided with a
tamper-evident ring 40 of the type described and claimed in
our international patent application PCT/GB93/02341
which published as W094/11267.i
Briefly, the tamper evident ring 40 is provided with
frangible joints 41 to the closure 12 and with flexible tabs
42 that abut against the underside of a flange 43 on the
container neck. The flexibility of the tabs 42 allows the
tamper-evident ring to snap over the flange on the conta finer
neck when the closure is first screwed down onto the
container neck. However, unscrewing the closure cap causes
the closure cap and tamper-evident ring to separate at the
frangible joints 41. To ensure that this separation occurs,
ratchet means 44 are provided on the container neck below
the flange 43 to block rotation of the tamper evident ring
in the direction of unscrewing of the closure, and thereby
apply a torsional force as well as tension across the
frangible joints 41 when the closure is unscrewed.
The assembly includes a safety feature to prevent the
possibility that the closure 10 might spin off controllably
under the internal pressure when a person begins to unscrew
the closure. In this embodiment, the safety feature is
provided by the arrangement of the threads 14 and 16, as
best seen in Figs. 3 to 5.
WO 95/05322 216 8 ~ ~ 2, pCT/GB94/01753
12
Each thread segment of the neck thread 14 has a
generally wide first portion 30 at its end closest to the
open end 24 of the neck 10, and a relatively narrow second
portion 32 which extends below the wide portion. The region
joining the wide portion 30 to the stem portion 32 is formed
generally with a step profile on its lower side to define a
first abutment surface 34. The abutment surface includes a
recess in the form of a concave profile (viewed in an axial
plane). The outermost corner 36 of the abutment surface
acts as a locating lip. The upper surface of the neck
thread segment is smooth and continuous between said first
and second portions.
Each thread segment of the closure thread 16 is shorter
than the corresponding segment of the neck thread 14 , and
has generally straight and parallel sides and rounded ends.
The width of each segment of the closure thread is
approximately the same as that of the narrow second portion
32 described above. The rounded end 38 of each closure
thread segment which is remote from the open end of the
closure 12 acts as a second abutment surface for engagement
with the first abutment surface 34 of the neck thread.
As best seen in Figs. 3 to 5, the spacing of the second
portions 32 of adjacent segments of the neck thread 14 is
greater than the cross-sectional width of the closure thread
segments. This permits a limited amount of axial movement
of the closure 12 on the neck 10 when the closure is in a
rotational position such that the closure thread segments
are between the second portions 32 of adjacent neck thread
segments. However, the spacing between the first portions
30 of adjacent neck thread segments is just wide enough to
pass the closure thread segment (see Fig. 5) but not wide
enough to permit substantial axial movement without
rotation.
In use, when closure 12 is in its closed position, the
arrangement of the threads will be as illustrated in Fig. 3.
If there is little or no pressure in the container, then as
the closure is unscrewed, the closure thread segments will
move initially in a circumferential direction until they
WO 95/05322 ~ ~ pCT/GB94/01753
13
bear against the smooth upper surfaces of the neck thread
segments (see Fig. 3), after which the closure thread
segments will ride up the smooth upper surfaces of the neck
thread segment (see Fig. 5) allowing the closure 12 to be
unscrewed freely from the neck 10.
However, if the container contents are pressurised, then
when the closure is unscrewed initially, the internal
pressure will act on the closure to "lift" or displace the
closure 12 axially in a direction emerging from the neck 10,
such displacement being allowed by the relatively wide
spacing of the second portions 32 of the adjacent neck
thread segments. Therefore, the closure thread segments
will remain in contact with the underside of the first
thread segments. From the moment the closure is moved from
the closed position (Figure 2), a clear vent passage is
created between the threads to release pressure. If the
closure continues to be unscrewed while under pressure, or
if the internal pressure is large enough to cause the
closure to begin to unscrew itself, then the end surfaces 38
of the closure thread segments will come into engagement
with the abutment surfaces 34 of the neck thread segments
thereby to block further rotation of the closure in the
unscrewing direction (see Fig. 4).
Thereafter, the closure 12 will be held in an
intermediate position on the container neck 10. The convex
shape of the upper ends of the closure threads 16 nests
within the recessed concave shape of the abutment surface
34. This provides a positive locating effect to prevent any
tendency for the neck and closure threads 14 and 16 to ride
past each other, for example, under extreme internal
pressure. It will be appreciated that the positive locating
effect will be stronger the higher the internal pressure
acting on the closure. The positive locating effect will
also depend on the exact shape of the abutment surface 32 on
the neck threads.
When the threads are in the condition shown in Fig. 4,
the closure 12 will be lifted sufficiently above the
container neck to release the seal formed by the first and
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W O 95/05322 ' ~ ~ ' p~.r'T/GB94/01753
14
second sealing surfaces and the ridge . The
internal pressure is vented by allowing gas to escape
between the neck and the closure. As best seen in Fig. 4,
the clear passage referred to already exists between the
threads 14,16 of the neck and the closure, through which
the pressure can escape. Additional vent passages 39 are
provided in the segments of the neck thread 14 and in the
segments of the closure thread 16. The additional vent
passages 39 are arranged such that they become aligned when
the threads are as shown in Fig. 4 to provide a further
route through which gas can escape.
Once the internal pressure has dropped to a safe level,
the closure 12 can be rotated to move the neck thread
segments past the projecting corners 36 of the closure
thread segments. The size and shape of the projecting
corners 36 control how difficult or easy it will be for a
person to release the first and second abutment surfaces 34
and 38 from engagement. For example, it may be necessary to
press the closure axially towards the container to release
the engagement of the second abutment surface 38 against the
f first abutment surface 34 . The closure 12 may also drop
down automatically under gravity when the internal pressure
is no longer great enough to maintain it in its displaced
condition.
Referring now to Fig. 6, a second embodiment of the
present invention has triangular cross section threads on at
least part of the container neck and closure. The closure
threads are not shown in Fig. 6 for the sake of clarity.
Likewise, vent passages similar to the vent passages 39
shown in Figs. 1-5 have been omitted for the sake of
clarity. The neck threads 51 are arranged to provide a
four-start one-quarter turn closing action. The neck
threads 51 each comprise an upper portion 52 having a
substantially trapezoidal cross section and a lower portion
53 having substantially triangular cross section. A step 54
between the upper and lower portions of the thread 51 on
the lower side of the thread 51 provides an abutment surface
for abutment against an end of the substantially triangular
W095/05322 ~~ PCT/GB94/01753
cross section closure thread when the closure is partially
unscrewed under pressure from the contents of the container.
The first portions 52 of the neck threads 51 abut radially
around the neck to define grooves 55 along which the
5 triangular cross section neck threads slide when removing
the closure after the pressure inside the container has been
released.
The trapezoidal shape of the first thread portions 52
and the triangular grooves 55 are shown more clearly in
10 cross section in Fig. 7. This drawing also shows the
triangular cross section threads 56 of the closure 57
located in the grooves 55.
Although the container neck and closure referred to in
the above embodiments are made of plastics, it will be
15 appreciated that one or both of the neck and closure may be
made from other materials. For example, the neck may be of
glass; the closure may be of metal.
It will further be appreciated that although the above
embodiment employs a seal turned between the lip of the
container neck and a layer of elastomer in the base of the
closure, other sealing means might be employed in modified
embodiments.
It is emphasised that the above description is merely
illustrative of a preferred embodiment of this invention,
and that modification of detail may be made without
departing from the scope and principles of this invention.
